US20180290738A1 - Constant-Velocity Joint Link with Reduced Axial Stiffness - Google Patents
Constant-Velocity Joint Link with Reduced Axial Stiffness Download PDFInfo
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- US20180290738A1 US20180290738A1 US16/006,552 US201816006552A US2018290738A1 US 20180290738 A1 US20180290738 A1 US 20180290738A1 US 201816006552 A US201816006552 A US 201816006552A US 2018290738 A1 US2018290738 A1 US 2018290738A1
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- link
- tension loop
- central portion
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/32—Rotors
- B64C27/37—Rotors having articulated joints
- B64C27/41—Rotors having articulated joints with flapping hinge or universal joint, common to the blades
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/32—Rotors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C29/00—Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft
- B64C29/0008—Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded
- B64C29/0016—Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded the lift during taking-off being created by free or ducted propellers or by blowers
- B64C29/0033—Aircraft capable of landing or taking-off vertically, e.g. vertical take-off and landing [VTOL] aircraft having its flight directional axis horizontal when grounded the lift during taking-off being created by free or ducted propellers or by blowers the propellers being tiltable relative to the fuselage
Definitions
- the present application generally relates to constant-velocity joints for aircraft rotors and specifically relates to a constant-velocity joint link having reduced stiffness.
- FIG. 1 A tiltrotor aircraft 11 having three-blade proprotors 13 A, 13 B driven by engines carried in nacelles 15 A, 15 B, respectively, is shown in FIG. 1 .
- joints In a gimbaled rotor, joints must be provided between the driveshaft that carries torque from the engine and the yoke that drives the blades, giving rise to a relatively complex hub assembly.
- An example of such an assembly used in proprotors is described generally in U.S. Pat. No. 4,804,352, assigned to Lord Corporation, which is incorporated by reference herein as if set forth in full and shown in FIGS. 2 through 5 .
- FIG. 2 shows a rotor assembly 17 , comprising hub assembly 19 and yoke 21 .
- Yoke 21 has three arms 23 that extend radially and are configured for rotor blades (visible in FIG. 1 ) to be attached thereto.
- Hub assembly 19 comprises an upper hub-spring plate 25 , lower hub-spring plate 27 , and a constant-velocity (CV) joint 29 carried between hub-spring plates 25 , 27 .
- CV constant-velocity
- a drive hub 31 has a splined opening 33 for receiving a splined driveshaft (not shown), and drive hub 31 is connected through pivoting linkage to yoke 21 .
- the pivoting linkage comprises three pairs of members, each pair having a link 35 and clevis 37 . Use of these links is described in detail in U.S. Pat. No. 5,186,686, assigned to Lord Corporation, which is incorporated by reference herein as if set forth in full.
- Each end of links 35 has a spherical laminated elastomeric bearing 39 , 41 , with the leading-end bearing 39 of each link 35 being connected to hub 31 and the trailing-end bearing 41 of each link 35 being connected to a clevis 37 .
- Clevises 37 are connected to hub-spring plates 25 , 27 with bolts 43 , and bolts 43 also fasten hub-spring plates 25 , 27 to each other and to yoke 21 .
- This provides a path for torque to be transferred from the driveshaft into drive hub 31 , though drive hub 31 into links 35 , through links 35 into devises 37 , through clevises 37 into bolts 43 and hub-spring plates 25 , 27 , and through bolts 43 and hub-spring plates 25 , 27 into yoke 21 for driving the blades.
- Hub-spring plates 25 , 27 cooperate to carry the thrust and shear loads for the rotor.
- FIG. 1 is an oblique view of a prior-art tiltrotor aircraft
- FIG. 2 is an enlarged oblique view of a portion of a rotor assembly of the aircraft of FIG. 1 ;
- FIG. 3 is an exploded oblique view of the portion of a rotor assembly of FIG. 2 ;
- FIG. 4 is an oblique view of the portion of a rotor assembly of FIG. 2 with some of the components being removed for ease of viewing;
- FIG. 5 is an oblique view of the portion of a rotor assembly of FIG. 2 with some of the components being removed for ease of viewing;
- FIG. 6 is an oblique view of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown in FIG. 2 ;
- FIG. 7 is an oblique view of the link of FIG. 6 with a tension loop having been removed;
- FIG. 8 is an oblique view of the tension loop of the link of FIG. 6 ;
- FIG. 9 is an oblique view of the bearing components of the link of FIG. 6 ;
- FIG. 10 is an oblique view of another embodiment of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown in FIG. 2 ;
- FIG. 11 is a side view of the link of FIG. 10 ;
- FIG. 12 is a top view of the link of FIG. 10 ;
- FIG. 13 is an oblique view of another embodiment of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown in FIG. 2 ;
- FIG. 14 is a side view of the link of FIG. 13 ;
- FIG. 15 is a top view of the link of FIG. 13 .
- FIG. 1 the rotor assemblies are shown in FIG. 1 in a horizontal orientation and in FIGS. 2 through 5 in a generally vertical orientation.
- components of the assembly may be described in relation to the vertical orientation, though it should be understood that this is for descriptive purposes only, as the orientation of the assembly will change during use.
- the system and method of the present application provides for an improved constant-velocity-joint drive link, which allows for a selected spring rate to be utilized in connecting the drive hub and the yoke.
- the oscillatory drive link load is influenced by the stiffness of the link in the drive direction, but the prior-art links were designed without taking into account the relationship between the link loads and the hub-spring loads.
- the improved links allow for tailoring of the relationship between the spring rate of the links and the lateral spring rate of the hub spring to minimize the loads in both parts.
- the prior-art link 35 has a unitary metal body 45 that comprises two bearing pockets 47 , 49 on opposite ends of body 45 .
- a leading bearing pocket houses leading bearing 39
- trailing bearing pocket 49 houses trailing bearing 41 .
- Trailing pocket 49 is longitudinally spaced from leading pocket 47 .
- Between pockets 47 , 49 is a thick web that connects pockets 47 , 49 and provides link 35 with high stiffness in the longitudinal direction, which is the direction of force as leading bearing 39 is driven by drive hub 31 . This causes link 35 to have an axial spring rate higher than necessary and causes high loads on link 35 and the hub spring assembly.
- FIGS. 6 through 15 illustrate three embodiments of an improved drive link for a constant-velocity joint, and these links may be configured as components of a link system for replacing links 35 and clevises 37 in rotor assemblies 13 A and 13 B of aircraft 11 of FIG. 1 , as shown in rotor hub assembly 17 of FIG. 2 .
- an improved drive link 51 comprises a circumferential, “racetrack”-style design, in which a tension loop 53 surrounds a bearing assembly 55 .
- Bearing assembly 55 comprises a leading bearing housing 57 and a trailing bearing housing 59 , with a leading bearing 61 located in leading housing 57 and a trailing bearing 63 located in trailing housing 59 .
- link 51 differs from prior-art link 35 in several ways, including construction materials and performance. As described above, link 35 is formed of metal, whereas link 51 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.
- Loop 53 which is shown removed from link 51 in FIG. 8 , is preferably formed as a continuous band from fiberglass-reinforced plastic and preferably created through winding fiber or tape a selected number of times about the exterior of bearing assembly 55 . Loop 53 has a selected axial spring rate that is determined by the number of fibers in the cross-section.
- Bearing assembly 55 is shown in FIG. 7 with tension loop 53 removed.
- Each bearing housing 57 , 59 has a spherically shaped bearing pocket 65 , 67 , respectively, for receiving one of bearings 61 , 63 , and bearing are shown removed from housing 57 , 59 in FIG. 9 .
- Bearings 61 , 63 are preferably laminated, elastomeric spherical bearings, and each has a central portion 69 for engaging either drive hub 31 or a clevis.
- Bearing housings 57 , 59 are preferably formed from metal, though housings 57 , 59 may be designed in various applications to allow them to be formed of composite or other appropriate materials.
- bearing assembly 55 also comprises a central flat-pad bearing 71 , or a similar structure, that is adhered on each end to housings 57 , 59 .
- Bearing 71 preferably comprises a plurality of elastomer pads 73 joined together, and bearing 71 provides a resilient, compressible structure between housings 57 , 59 .
- FIG. 8 shows tension loop 53 removed from link 51 .
- loop 53 has a constant cross-sectional shape, though loop 53 may be formed to have various shapes for tailoring loop 53 to a particular application.
- loop 53 may have thinned sections to provide for clearance of adjacent components or, in appropriate applications, to provide for tailoring of bending or torsional rigidity.
- Loop 53 has an outer surface 75 , an inner surface 77 , and side surfaces 79 .
- surface 75 , 77 , 79 are continuous, smooth surfaces, though other embodiments may be configured to have different characteristics.
- Improved link 51 allows for reduced link stiffness in tension by replacing the stiff central structure of link 35 with relatively thin loop 53 that connects bearing pockets 57 , 59 . Though the ends of flat-pad bearing 71 are adhered to housings 57 , 59 , tension forces created between housings 57 , 59 as drive hub 31 drives leading bearing 61 are carried by the fibers of loop 53 . Whereas link 51 having a lower spring rate equals a lower load, the spring rate must be maintained at a minimum level, as there must be sufficient stiffness to carry the positive torque transmitted from drive hub 31 .
- link 51 must be strong enough to withstand transient negative torque, which occurs due to the interconnection between the drive systems of the rotors. These transients may be approximately 1 ⁇ 6 to 1 ⁇ 4 of the positive torque load. While composites excel when used in tension, such as experienced with positive torque, negative torque leads to compression of link 51 . Therefore, link 51 must be engineered to handle both the positive and negative torque loads, which may be the determining factor in choosing a material for forming bearing housings 57 , 59 . A metal construction is preferred to ensure sufficient strength of link 51 in applications where it will experience negative torque.
- flat-pad bearing 71 provides for a compressible structure between housings 57 , 59 to absorb some of the compression load between housings 57 , 59 created by negative torque.
- a preferred method of constructing link 51 includes compressing bearing assembly 55 prior to forming loop 53 , allowing loop 53 to be preloaded after assembly of link 51 .
- Housings 57 , 59 are formed around bearings 61 , 63 , respectively, and housings are joined to the ends of flat-pad bearing 71 .
- Bearing assembly 55 is then compressed by moving housings 57 , 59 toward each other a selected amount, and then loop 53 is formed by winding individual fibers or composite tape around outer surface 81 of housing 57 and outer surface 83 of housing 59 .
- An optional thin elastomer sheet (not shown) may be located between inner surface 77 of loop 53 and outer surfaces 81 , 83 to protect loop 53 from damage during use.
- optional elastomer wedges 85 may be inserted between the inner ends of housings 57 , 59 near flat-pad bearing 71 to provide additional protection to loop 53 .
- Loop 53 is prevented from misalignment due to lateral movement relative to housings 57 , 59 by planar protrusions 87 that extend from the ends of housings 57 , 59 .
- “Kinematic pinch” is binding that is present during flapping in a 3-link hub design and that causes a twice per revolution (in the rotating system) in-plane displacement of the centering hub spring, and the value for kinematic pinch can be calculated (not shown).
- the resulting values of 10,286 lbs for the link load and 15,429 lbs for the hub-spring load can be compared to those calculated for an improved link, such as link 51 , having a reduced spring rate.
- a 10% reduction in the link spring rate with all other variables remaining unchanged produces a value of 9,672 lbs for the link load and 14,507 lbs for the hub-spring load, a 6% reduction for each.
- a 20% reduction in link spring rate results in a 12.5% reduction in each load.
- the hub spring rate may also be selected for a minimum value by using these equations to choose the best spring rates of each component in the system.
- an improved drive link 89 comprises a circumferential, “racetrack”-style design, in which a tension loop 91 is formed as a continuous band and surrounds a leading bearing pocket 93 and a trailing bearing pocket 95 .
- Leading bearing 97 is located in leading pocket 93
- trailing bearing 99 is located in trailing pocket 95
- bearings 97 , 99 are spherical laminated elastomeric bearings.
- link 89 may be designed as part of a replacement structure for prior-art link 35 and clevis 37 .
- Link 89 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.
- Loop 91 is preferably formed from fiberglass-reinforced plastic and preferably created by winding a selected number of times about the exterior of link 89 . This construction provides link 89 with a selected axial spring rate that is determined by the number of fibers in the cross-section.
- a central portion 101 comprises two pocket walls 103 , 105 that cooperate with loop 91 to define bearing pockets 93 , 95 , respectively.
- central portion 101 comprises an aperture 107 defined by pocket walls 103 , 105 and that extends laterally through link 89 .
- an optional web (not shown) may be formed between pocket walls 103 , 105 .
- Central portion 101 may be formed of a composite, metal, or other appropriate material. If formed from a composite, loop 91 and central portion 101 may be constructed together to form an integrated part. For any material, central portion 101 may be formed as a separate component onto which loop 91 is assembled, or loop 91 may be formed by winding fibers about central portion 101 .
- Link 89 minimizes the link stiffness by replacing the stiff central structure of link 35 with the relatively thin upper strap 109 and lower strap 111 of loop 91 that connect bearing pockets 93 , 95 . Straps 109 , 111 are made as long as possible and as thin as possible to minimize the spring rate. In the embodiment shown in FIGS. 10 through 12 , having aperture 107 in central portion 101 ensures that all of the axial forces exerted on link 89 pass between bearings only through the fibers of loop 91 . Whereas link 89 having a lower spring rate equals a lower load, the spring rate must be maintained at a minimum level, as there must be sufficient stiffness to carry the positive torque transmitted from the drive hub.
- link 89 must be strong enough to withstand transient negative torque. Therefore, link 89 must be engineered to handle both the positive and negative torque loads, which may be the determining factor in choosing a material for forming central portion 101 . A metal construction may be preferred to ensure sufficient strength of link 89 in applications where it will experience negative torque.
- Drive link 113 comprises a circumferential, “dog bone”-style loop 115 formed as a continuous band and surrounding a leading bearing pocket 117 and a trailing bearing pocket 119 .
- a leading bearing 121 is located in leading pocket 117
- a trailing bearing 123 is located in trailing pocket 119 .
- link 113 can be designed as part of a replacement structure for prior-art link 35 and clevis 37 .
- Link 113 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.
- Loop 115 is preferably formed from fiberglass-reinforced plastic and preferably created by winding a selected number of times about the exterior of link 113 .
- Loop 115 has a varying cross-sectional shape. This construction provides link 113 with a selected overall axial spring rate that is determined by the number of fibers in the cross-section, but the varying cross-sectional shape allows for the tailoring of the thickness of upper strap 125 and lower strap 127 .
- Central portion 129 comprises two pocket walls 131 , 133 that cooperate with loop 115 to define bearing pockets 117 , 119 , respectively.
- central portion 129 comprises a stiff web 135 extending between straps 125 , 127 and pocket walls 131 , 133 .
- an optional aperture may be formed between pocket walls 131 , 133 .
- Central portion 129 may be formed of a composite, metal, or other appropriate material. If formed from a composite, loop 115 and central portion 129 may be constructed together to form an integrated part. For any material, central portion 129 may be formed as a separate component onto which loop 115 is assembled, or loop 115 may be formed by winding fibers about central portion 129 .
- link 113 minimizes the link stiffness by comprising relatively thin straps 125 , 127 of loop 115 .
- straps 125 , 127 are thinned, resulting in the “dog bone”-style configuration.
- axial forces exerted on link 113 pass between bearings through both the fibers of loop 115 and through web 135 .
- the drive links of the present application provide significant advantages, including providing for a lighter CV joint, lower link loads, and lower hub spring loads.
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Abstract
Description
- The present application generally relates to constant-velocity joints for aircraft rotors and specifically relates to a constant-velocity joint link having reduced stiffness.
- Designs of rotors and propellers for aircraft are often extremely complex. A large number of factors must be taken into account, including flexure of the rotor under heavy loads and the required motions of the rotor blades with respect to the drive mechanism. The considerations for proprotors, used as both propellers and rotors in aircraft such as a tiltrotor aircraft, can be more complex than usual. A
tiltrotor aircraft 11 having three-blade proprotors nacelles FIG. 1 . - In a gimbaled rotor, joints must be provided between the driveshaft that carries torque from the engine and the yoke that drives the blades, giving rise to a relatively complex hub assembly. An example of such an assembly used in proprotors is described generally in U.S. Pat. No. 4,804,352, assigned to Lord Corporation, which is incorporated by reference herein as if set forth in full and shown in
FIGS. 2 through 5 . -
FIG. 2 shows arotor assembly 17, comprisinghub assembly 19 andyoke 21. Yoke 21 has threearms 23 that extend radially and are configured for rotor blades (visible inFIG. 1 ) to be attached thereto.Hub assembly 19 comprises an upper hub-spring plate 25, lower hub-spring plate 27, and a constant-velocity (CV)joint 29 carried between hub-spring plates - Referring now specifically to
FIGS. 3 through 5 , adrive hub 31 has asplined opening 33 for receiving a splined driveshaft (not shown), and drivehub 31 is connected through pivoting linkage to yoke 21. The pivoting linkage comprises three pairs of members, each pair having alink 35 andclevis 37. Use of these links is described in detail in U.S. Pat. No. 5,186,686, assigned to Lord Corporation, which is incorporated by reference herein as if set forth in full. - Each end of
links 35 has a spherical laminated elastomeric bearing 39, 41, with the leading-end bearing 39 of eachlink 35 being connected tohub 31 and the trailing-end bearing 41 of eachlink 35 being connected to aclevis 37.Clevises 37 are connected to hub-spring plates bolts 43, andbolts 43 also fasten hub-spring plates drive hub 31, though drivehub 31 intolinks 35, throughlinks 35 intodevises 37, throughclevises 37 intobolts 43 and hub-spring plates bolts 43 and hub-spring plates yoke 21 for driving the blades. Hub-spring plates - The novel features believed characteristic of the system of the present application are set forth in the appended claims. However, the system itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:
-
FIG. 1 is an oblique view of a prior-art tiltrotor aircraft; -
FIG. 2 is an enlarged oblique view of a portion of a rotor assembly of the aircraft ofFIG. 1 ; -
FIG. 3 is an exploded oblique view of the portion of a rotor assembly ofFIG. 2 ; -
FIG. 4 is an oblique view of the portion of a rotor assembly ofFIG. 2 with some of the components being removed for ease of viewing; -
FIG. 5 is an oblique view of the portion of a rotor assembly ofFIG. 2 with some of the components being removed for ease of viewing; -
FIG. 6 is an oblique view of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown inFIG. 2 ; -
FIG. 7 is an oblique view of the link ofFIG. 6 with a tension loop having been removed; -
FIG. 8 is an oblique view of the tension loop of the link ofFIG. 6 ; -
FIG. 9 is an oblique view of the bearing components of the link ofFIG. 6 ; -
FIG. 10 is an oblique view of another embodiment of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown inFIG. 2 ; -
FIG. 11 is a side view of the link ofFIG. 10 ; -
FIG. 12 is a top view of the link ofFIG. 10 ; -
FIG. 13 is an oblique view of another embodiment of an improved constant-velocity-joint drive link configured for use in a rotor assembly like that shown inFIG. 2 ; -
FIG. 14 is a side view of the link ofFIG. 13 ; and -
FIG. 15 is a top view of the link ofFIG. 13 . - While the system of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the system to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application as defined by the appended claims.
- Illustrative embodiments of the system of the present application are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
- In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” “inboard,” “outboard,” “leading,” “trailing” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.
- For example, the rotor assemblies are shown in
FIG. 1 in a horizontal orientation and inFIGS. 2 through 5 in a generally vertical orientation. In the following description, components of the assembly may be described in relation to the vertical orientation, though it should be understood that this is for descriptive purposes only, as the orientation of the assembly will change during use. - The system and method of the present application provides for an improved constant-velocity-joint drive link, which allows for a selected spring rate to be utilized in connecting the drive hub and the yoke. The oscillatory drive link load is influenced by the stiffness of the link in the drive direction, but the prior-art links were designed without taking into account the relationship between the link loads and the hub-spring loads. The improved links allow for tailoring of the relationship between the spring rate of the links and the lateral spring rate of the hub spring to minimize the loads in both parts.
- Referring again to
FIG. 5 , the prior-art link 35 has aunitary metal body 45 that comprises twobearing pockets body 45. A leading bearing pocket houses leading bearing 39, and trailing bearingpocket 49 houses trailing bearing 41.Trailing pocket 49 is longitudinally spaced from leadingpocket 47. Betweenpockets pockets link 35 with high stiffness in the longitudinal direction, which is the direction of force as leadingbearing 39 is driven bydrive hub 31. This causeslink 35 to have an axial spring rate higher than necessary and causes high loads onlink 35 and the hub spring assembly. -
FIGS. 6 through 15 illustrate three embodiments of an improved drive link for a constant-velocity joint, and these links may be configured as components of a link system for replacinglinks 35 andclevises 37 inrotor assemblies aircraft 11 ofFIG. 1 , as shown inrotor hub assembly 17 ofFIG. 2 . - Referring to
FIGS. 6 through 9 , an improveddrive link 51 comprises a circumferential, “racetrack”-style design, in which atension loop 53 surrounds abearing assembly 55.Bearing assembly 55 comprises a leading bearinghousing 57 and a trailing bearinghousing 59, with a leading bearing 61 located in leadinghousing 57 and a trailing bearing 63 located in trailinghousing 59. - Though designed to function in a similar way as part of a replacement structure,
link 51 differs from prior-art link 35 in several ways, including construction materials and performance. As described above, link 35 is formed of metal, whereaslink 51 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.Loop 53, which is shown removed fromlink 51 inFIG. 8 , is preferably formed as a continuous band from fiberglass-reinforced plastic and preferably created through winding fiber or tape a selected number of times about the exterior of bearingassembly 55.Loop 53 has a selected axial spring rate that is determined by the number of fibers in the cross-section. - Bearing
assembly 55 is shown inFIG. 7 withtension loop 53 removed. Each bearinghousing pocket bearings housing FIG. 9 .Bearings central portion 69 for engaging eitherdrive hub 31 or a clevis.Bearing housings housings loop 53 andhousings assembly 55 also comprises a central flat-pad bearing 71, or a similar structure, that is adhered on each end tohousings Bearing 71 preferably comprises a plurality ofelastomer pads 73 joined together, and bearing 71 provides a resilient, compressible structure betweenhousings -
FIG. 8 showstension loop 53 removed fromlink 51. In the embodiment shown,loop 53 has a constant cross-sectional shape, thoughloop 53 may be formed to have various shapes for tailoringloop 53 to a particular application. For example,loop 53 may have thinned sections to provide for clearance of adjacent components or, in appropriate applications, to provide for tailoring of bending or torsional rigidity.Loop 53 has anouter surface 75, aninner surface 77, and side surfaces 79. In the embodiment shown,surface -
Improved link 51 allows for reduced link stiffness in tension by replacing the stiff central structure oflink 35 with relativelythin loop 53 that connects bearingpockets pad bearing 71 are adhered tohousings housings drive hub 31drives leading bearing 61 are carried by the fibers ofloop 53. Whereaslink 51 having a lower spring rate equals a lower load, the spring rate must be maintained at a minimum level, as there must be sufficient stiffness to carry the positive torque transmitted fromdrive hub 31. - In addition, link 51 must be strong enough to withstand transient negative torque, which occurs due to the interconnection between the drive systems of the rotors. These transients may be approximately ⅙ to ¼ of the positive torque load. While composites excel when used in tension, such as experienced with positive torque, negative torque leads to compression of
link 51. Therefore, link 51 must be engineered to handle both the positive and negative torque loads, which may be the determining factor in choosing a material for formingbearing housings link 51 in applications where it will experience negative torque. In the embodiment shown, flat-pad bearing 71 provides for a compressible structure betweenhousings housings - A preferred method of constructing
link 51 includes compressingbearing assembly 55 prior to formingloop 53, allowingloop 53 to be preloaded after assembly oflink 51.Housings bearings pad bearing 71. Bearingassembly 55 is then compressed by movinghousings loop 53 is formed by winding individual fibers or composite tape aroundouter surface 81 ofhousing 57 andouter surface 83 ofhousing 59. An optional thin elastomer sheet (not shown) may be located betweeninner surface 77 ofloop 53 andouter surfaces loop 53 from damage during use. Also,optional elastomer wedges 85 may be inserted between the inner ends ofhousings pad bearing 71 to provide additional protection toloop 53.Loop 53 is prevented from misalignment due to lateral movement relative tohousings planar protrusions 87 that extend from the ends ofhousings - The amount of reduction in forces due to mechanism kinematics experienced by
link 51 that can be achieved by reducing the axial spring rate can be calculated using the equations shown below, wherein: -
- “Kinematic pinch” is binding that is present during flapping in a 3-link hub design and that causes a twice per revolution (in the rotating system) in-plane displacement of the centering hub spring, and the value for kinematic pinch can be calculated (not shown).
- The equations for approximating these loads on the link and spring hub are:
-
- To determine the loads on the link and hub spring, the following calculations include a calculated kinematic pinch value for 10 degrees of flapping and sample spring rate values for
link 35 and an example hub spring: -
- The resulting values of 10,286 lbs for the link load and 15,429 lbs for the hub-spring load can be compared to those calculated for an improved link, such as
link 51, having a reduced spring rate. For example, a 10% reduction in the link spring rate with all other variables remaining unchanged produces a value of 9,672 lbs for the link load and 14,507 lbs for the hub-spring load, a 6% reduction for each. A 20% reduction in link spring rate results in a 12.5% reduction in each load. - Whereas these calculations show the effect of reducing the spring rate of
link 51, the hub spring rate may also be selected for a minimum value by using these equations to choose the best spring rates of each component in the system. - Referring to
FIGS. 10 through 12 , another embodiment of animproved drive link 89 comprises a circumferential, “racetrack”-style design, in which atension loop 91 is formed as a continuous band and surrounds a leadingbearing pocket 93 and a trailingbearing pocket 95. Leadingbearing 97 is located in leadingpocket 93, and trailingbearing 99 is located in trailingpocket 95, andbearings - As with
link 51, link 89 may be designed as part of a replacement structure for prior-art link 35 andclevis 37.Link 89 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.Loop 91 is preferably formed from fiberglass-reinforced plastic and preferably created by winding a selected number of times about the exterior oflink 89. This construction provideslink 89 with a selected axial spring rate that is determined by the number of fibers in the cross-section. - A
central portion 101 comprises twopocket walls loop 91 to define bearingpockets central portion 101 comprises anaperture 107 defined bypocket walls link 89. Alternatively, an optional web (not shown) may be formed betweenpocket walls Central portion 101 may be formed of a composite, metal, or other appropriate material. If formed from a composite,loop 91 andcentral portion 101 may be constructed together to form an integrated part. For any material,central portion 101 may be formed as a separate component onto whichloop 91 is assembled, orloop 91 may be formed by winding fibers aboutcentral portion 101. -
Link 89 minimizes the link stiffness by replacing the stiff central structure oflink 35 with the relatively thinupper strap 109 andlower strap 111 ofloop 91 that connect bearingpockets Straps FIGS. 10 through 12 , havingaperture 107 incentral portion 101 ensures that all of the axial forces exerted onlink 89 pass between bearings only through the fibers ofloop 91. Whereaslink 89 having a lower spring rate equals a lower load, the spring rate must be maintained at a minimum level, as there must be sufficient stiffness to carry the positive torque transmitted from the drive hub. - In addition, as described above, link 89 must be strong enough to withstand transient negative torque. Therefore, link 89 must be engineered to handle both the positive and negative torque loads, which may be the determining factor in choosing a material for forming
central portion 101. A metal construction may be preferred to ensure sufficient strength oflink 89 in applications where it will experience negative torque. - Another embodiment of an improved link according to the present application is shown in
FIGS. 13 through 15 .Drive link 113 comprises a circumferential, “dog bone”-style loop 115 formed as a continuous band and surrounding a leadingbearing pocket 117 and a trailingbearing pocket 119. A leadingbearing 121 is located in leadingpocket 117, and a trailingbearing 123 is located in trailingpocket 119. Likelinks art link 35 andclevis 37. -
Link 113 is able to be formed, at least in part, from composite materials, such as fiberglass or carbon-fiber composites.Loop 115 is preferably formed from fiberglass-reinforced plastic and preferably created by winding a selected number of times about the exterior oflink 113.Loop 115 has a varying cross-sectional shape. This construction provideslink 113 with a selected overall axial spring rate that is determined by the number of fibers in the cross-section, but the varying cross-sectional shape allows for the tailoring of the thickness ofupper strap 125 andlower strap 127. -
Central portion 129 comprises twopocket walls loop 115 to define bearingpockets central portion 129 comprises astiff web 135 extending betweenstraps pocket walls pocket walls Central portion 129 may be formed of a composite, metal, or other appropriate material. If formed from a composite,loop 115 andcentral portion 129 may be constructed together to form an integrated part. For any material,central portion 129 may be formed as a separate component onto whichloop 115 is assembled, orloop 115 may be formed by winding fibers aboutcentral portion 129. - Like
link 89, link 113 minimizes the link stiffness by comprising relativelythin straps loop 115. However, straps 125, 127 are thinned, resulting in the “dog bone”-style configuration. In the embodiment shown inFIGS. 13 through 15 , axial forces exerted onlink 113 pass between bearings through both the fibers ofloop 115 and throughweb 135. - The drive links of the present application provide significant advantages, including providing for a lighter CV joint, lower link loads, and lower hub spring loads.
- The particular embodiments disclosed above are illustrative only, as the application may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below.
Claims (18)
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US16/006,552 US11066157B2 (en) | 2013-04-29 | 2018-06-12 | Constant-velocity joint link with reduced axial stiffness |
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US13/872,480 US9994311B2 (en) | 2013-04-29 | 2013-04-29 | Constant-velocity joint link with reduced axial stiffness |
US16/006,552 US11066157B2 (en) | 2013-04-29 | 2018-06-12 | Constant-velocity joint link with reduced axial stiffness |
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US13/872,480 Continuation US9994311B2 (en) | 2013-04-29 | 2013-04-29 | Constant-velocity joint link with reduced axial stiffness |
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US20180290738A1 true US20180290738A1 (en) | 2018-10-11 |
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US16/006,552 Active 2033-11-18 US11066157B2 (en) | 2013-04-29 | 2018-06-12 | Constant-velocity joint link with reduced axial stiffness |
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US13/872,480 Active 2035-07-28 US9994311B2 (en) | 2013-04-29 | 2013-04-29 | Constant-velocity joint link with reduced axial stiffness |
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Families Citing this family (9)
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US9657816B2 (en) * | 2013-11-01 | 2017-05-23 | Bell Helicopter Textron Inc. | Drive link for tiltrotor rotor system |
US9701403B2 (en) * | 2014-02-18 | 2017-07-11 | Bell Helicopter Textron Inc. | Broad goods composite yoke for rotor system |
USD808328S1 (en) * | 2016-09-14 | 2018-01-23 | Bell Helicopter Textron Inc. | Foldable tiltrotor aircraft |
EP3755623A1 (en) * | 2018-05-08 | 2020-12-30 | AVX Aircraft Company | Rotor hub |
USD974277S1 (en) | 2018-11-15 | 2023-01-03 | Textron Innovations, Inc. | Aircraft payload enclosure |
USD909278S1 (en) | 2018-11-15 | 2021-02-02 | Bell Helicopter Textron Inc. | Foldable tiltrotor aircraft |
USD909949S1 (en) | 2018-11-15 | 2021-02-09 | Bell Helicopter Textron Inc. | Tiltrotor aircraft |
USD974276S1 (en) | 2018-11-15 | 2023-01-03 | Textron Innovations, Inc. | Aircraft spinner |
CN115924071A (en) * | 2023-03-13 | 2023-04-07 | 扬州平航航空动力技术有限公司 | Tilt rotor aircraft hub system |
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JPS51143158A (en) * | 1975-06-04 | 1976-12-09 | Toyota Motor Corp | Flexible coupling for power transmission |
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-
2013
- 2013-04-29 US US13/872,480 patent/US9994311B2/en active Active
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2018
- 2018-06-12 US US16/006,552 patent/US11066157B2/en active Active
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US20140322010A1 (en) | 2014-10-30 |
US11066157B2 (en) | 2021-07-20 |
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